This invention relates to novel amide- and urea-modified liquid diphenylmethane diisocyanate compositions and to a process for the preparation of these novel amide-modified liquid diisocyanate compositions.
Polyisocyanate compositions exhibiting low viscosities and high functionalities and a process for their preparation are disclosed in U.S. Pat. No. 6,730,405. These polyisocyanate compositions may be reacted with a compound comprising a mobile hydrogen, which are also known as masking agents. Masking agents are described as having at least one functional group carrying a mobile (or reactive) hydrogen, and the functional group should have a pKa of at least 4 to less than or equal to 14.
U.S. Pat. No. 6,475,366 discloses cationically electrodepositable coating compositions. These coating compositions comprise as a cross-linking agent, a blocked polyisocyanate having at least 0.1 blocked isocyanate group represented by the formula:
in which R1 represents a hydrogen atom, or a methyl, ethyl or propyl group; and R2 represents a methyl or ethyl group. One of the coating compositions described comprises a cationic resin having an active hydrogen group capable of reacting an isocyanate group as a base resin and the blocked polyisocyanate described above as an external cross-linking agent. Another coating composition as described in U.S. Pat. No. 6,475,366 is a thermosetting cationically electrodepositable coating composition comprise as the base resin, a cationic resin of a self cross-linking type having both the blocked isocyanate group as set forth above and an active hydrogen group in a molecule.
It has surprisingly been found that diisocyanates which are modified with amides as described herein are low viscosity liquid products which are storage stable at room temperature. It has also been found that these modified diisocyanates exhibit lower freezing points than the corresponding unmodified diisocyanates. Advantages of these modified diisocyanates include the ability of store and use them in processes without the need to maintain a >25° C. storage temperature.